I accept this challenge of finding 10,000 waterfalls whether they half an inch to 5000 feet in the air. You cannot stop me Blizzard because I'm going to do it before your developers make it, and I know it makes no sense but it does. >

My gut feeling says the waterfall number is a placeholder, we've seen it before with achievements. They just set it to a crazy high number and then figure out what it's supposed to be.

Exactly this. Every single person commenting about "10,000 waterfalls" clearly doesn't remember (or never even looked at) the proposed achievements for 4.3 while it was still on the PTR. [Eclipse] required you to kill 10,000 of the orbs before killing the boss, until they updated it later to the proper number. 10,000 is just Blizzard's placeholder number. They'll update it to the proper number of waterfalls when they send a crew of people to go back and find every single waterfall on Pandaria to get the exact number.

I really hope the realm first challenge mode achievements are guild-based and not personal. Why target a feature toward heroic raiders and then only reward the 5 people who play the FOTM classes with the shiny feat of strength?

One of the things I felt Cata did right was moving the realm first "defeat X boss" achievements to guild achievements, so that everyone (benched players, players who switched to their arcane mage alt, players who had to miss the raid due to real life, etc.) still felt like they contributed. Personal realm first kill achievements were nothing but drama...

I really hope the realm first challenge mode achievements are guild-based and not personal. Why target a feature toward heroic raiders and then only reward the 5 people who play the FOTM classes with the shiny feat of strength?

I don't really see how the challenge modes are targeted at heroic raiders more than anyone else. Unless I severely misunderstood the concept, all that heroic raid gear isn't going to be an advantage to them at all. I'm sure they'll still GET them in the end, due to the drive to do so, but I imagine the competition will be much, much closer on the world and server stages than the heroic raid racers are just due to the fact that the heroic raiders will be putting most of their time and energy into the world/region firsts instead of the "server five man firsts"